AASHTO TP130:18(2020) Standard Method of Test for Producing Draw Down Panels and Measuring the Coefficient of Retroreflected Luminance (RL) of Pavement Markings in a Laboratory Panel.
4.1. This test procedure is used to predict the retroreflectivity of M 247, Type! glass beads in waterborne paint using a laboratory simulation of a field striping operation. Measured quantities of glass beads are dropped on top of a repeatable, uniform thickness of paint on top of a glass panel. When the paint is dry (after 24 hours), the retroreflectivity is measured using a 30 m geometry portable retroreflectometer.
One of the characteristics of a pavement marking is the
of retro reflected luminance,
R,. Under identical conditions of headlight illumination
and driver
viewing, larger values of R,.
correspond to higher levels of visual performance at corresponding
6.1. For waterborne paint, water for clean up;
6.2. 4 in. draw down bar; thickness capability from 15-30 mils (375-750 microns);
6.3. FIat substrate 6 by 24 in. made of 1/8 in. glass, aluminum, or slate;
6.4. Support fixture to hold substrate firmly in place during draw down;
6.5. Balance to 0.01 g accuracy;
6.6. Splitters to obtain representative glass bead sample (large 16:1, small 1: 1);
6.7. Weighing dishes and containers for beads and paint:
6.8. Bead drop box (see Figure 1) with dimensions of approximately 5I2 by in. by 14 in. (producing a 4 by 18 in. stripe) filled with 10 layers of in. screening spaced I in. apart, with support bar to hold beads in swivel mounted on top:
6.9. Reflectometer, 30 m geometry based on retrorellective measurements made with portable hand- operated instruments in compliance with ASTM E1710;
6.10. Paint film thickness gauge, 5-30 mit (125-750 microns); and Magnifying glass to check glass bead embedment.
A representative sample of glass beads meeting the requirements of M 247, Type 1, should he
taken following T 346 procedures. The sampling shall be random in the following ratios: 100 lb
(45 kg) of sample (in full bags) per 10,000 lb (4,535 kg) shipped. Upon arrival, material shall be
reduced in a sample splitter to a size of approximately 2.2 lb (1 kg).
The draw down procedure must he calibrated to ensure the correct thickness of paint is applied. The retroreflectometer must he calibrated in accordance with the manufacturer’s instructions. The retroreflectivity is very dependent on the paint formula in addition to the glass bead quality. Use a control paint to compare glass head retroreflectivity (Sherwin Williams TM2 152 White). Note 1—Use of this specific control product was chosen by NCHRP research team to minimize the test variables and compare testing and final retroreflection performance. Users could consider alternate control traffic paints to suit their specific needs.AASHTO TP130 pdf download.